Curves are used to join data points
Joins points using smooth curves, rather than straight lines.
Points are joined with computed (cubic) Bezier curves, where the smoothness is determined by the ‘flexibility’ parameter which may vary between zero (which joins the points with straight lines) to approx 12. The default value of 3 will normally give reasonable results. High values may start to draw loops and other artifacts on very noisy data series.
See also ...